by Kent Wallace

Returning water to the pond has largely been from a waterfall or stream but modern circulation techniques and higher turnover rates have created methods of circulation, which improve water quality and clarity.

The concept of rotating water around the bottom drain or drains in a circling “vortex” pattern has become the standard. The rotational speed we are
trying to achieve is slow at approximately 1ft/30cm per second and the object is not to create a whirlpool effect but to improve flow. The improved flow characteristics prevent un-circulated or stagnate areas from forming and breeding anaerobic activity.

TPR, GPR and VPR One small TPR (tangential pond return) flowing water at an angle can rotate a circular pond quite effectively at a rate of 450gal/
1703ltr per hour or less, but square, rectangular or uneven shapes will require more returns and higher flow rates to direct the flow in directions the pond shape can not do on its own. For instance a square pond might have a return in each corner to change the direction of water flow as the water nears the right angle of the perpendicular wall. A two drain system would have GPRs (gap pond returns) to direct the water between the drains and angled TPRs on the opposite wall and ends of the pond to cause water around each drain to rotate in opposite directions like a set of gears.
(Figure 1)

The number of returns and flow rate of each will be determined by the pond size, depth and overall flow pattern. It is important to locate skimmers and mid-water drains in positions that are at the end of the waters flow path. This is not necessarily straight across from a waterfall. A TPR pushing incoming water away from the skimmer prevents the freshly filtered water from flowing directly back into the skimmer this causes the water to flow completely around the pond before exiting. (Figure 2)

Mechanical Clamps

The pond returns must be mechanically clamped or sealed to the pond liner. When polyurea or other liquid applied products are used to seal the surface of a concrete pond the coating must also be mechanically clamped to the return piping. Several types of returns have been used over time. (Image 1)

From left to right the first is a 2in/50mm shower drain with a threaded insert that clamps over the liner. Next is a polyurethane bulkhead with the threads toward the pond side so the nut can be secured over the liner. These are often used with a large plastic washer to help spread the load evenly over a larger diameter. The third is a “Wedgelock” design that is used for liquid “roll on” or spray applied surfaces like polyurea. There are other types of tank connectors that can also be used for returns perpendicular to the pond wall but for angled returns there are two types currently available. The original angled return was PVC plate plastic welded to a section of pipe with a screw on flange that clamped the liner. (Image 2)

Currently DreamPond makes a molded version of both the straight and 45 degree angled return of very high quality without the risk of a welded connection and Living Water Solutions makes the “Wedgelock” return that can be cut to virtually any angle for use with polyurea and other liquid liner application over concrete. (Image 3) The “Wedgelock” is a flangeless termination that locks the liquid liner internally but cannot be used for EPDM liner whereas the DreamPond is well suited for the EPDM liner.

You Could Use Some Air

Air diffusers mounted on top of bottom drain domes are also a great way to increase pond circulation. The rising column of air draws a huge volume of water upward with it pulling water along the bottom. (Figure 3) The pattern of water flow looks much like the magnetic pattern around the earth. This is a high
volume flow and moves much more water than most current jets. Many times these are placed on timers to come on at specific times during the day or night. The huge volume of air and turbulent pond surface created by air diffusers makes fish viewing difficult in smaller ponds but in larger ponds it’s not usually an issue.

Conclusion

Armed with all these inlet and circulation options a ponds water quality becomes much more manageable when these options are used together as part of the
overall system. The increase in water quality through the prevention of stagnate areas of anaerobic activity creates a much healthier environment for your fish.